Data from patients receiving five doses of SEL-212 expected to be presented at Q3 medical conference

Phase 3 trial planned to begin in 2018

Selecta Biosciences, Inc. (NASDAQ:SELB), a clinical-stage biopharmaceutical company focused on unlocking the full potential of biologic therapies by mitigating unwanted immunogenicity, today presented new data from patients receiving SEL-212 for the treatment of chronic severe gout at the Pan American League of Associations for Rheumatology (PANLAR) 2018 Congress in Buenos Aires, Argentina.

SEL-212 is designed to be the first non-immunogenic version of uricase, which would allow for the effective and safe administration of multiple doses with concurrent mitigation of anti-drug antibodies (ADAs) against the pegsiticase enzyme. The data reported today at PANLAR consisted of patients that received three monthly doses of SEL-212, up to 0.15 mg/kg of SVP-Rapamycin in combination with 0.2 or 0.4 mg/kg of pegsiticase, followed by two monthly doses of pegsiticase alone. Approximately 75% of evaluable patients maintained serum uric acid level control below 6 mg/dl during the initial three months of therapy with concurrent mitigation of ADAs against the pegsiticase enzyme. Furthermore, 91% of patients dosed with pegsiticase alone in month four after the initial three monthly doses of SEL-212 maintained serum uric acid control demonstrating the potential of SVP technology for the induction of immune tolerance.

“We are very pleased by the clinical activity seen in the data presented today at PANLAR, not only in SEL-212’s ability to control serum uric acid levels but also in the reduced incidence of gout flares compared to the current FDA-approved uricase. We believe that SEL-212 has the potential to change the treatment paradigm for patients with chronic severe gout since there remains a high unmet need for a monthly-dosed therapy that can provide better and sustained serum uric acid control in these patients. Today’s reported data show that approximately 75% of evaluable patients maintained serum uric acid control through three months,” said Werner Cautreels, Ph.D., President and CEO of Selecta. “We plan to present data from patients receiving five monthly SEL-212 doses at an upcoming medical meeting in the third quarter of this year. We expect these results will expand the 3-month SEL-212 clinical activity shown in today’s PANLAR data across the entire 5-month treatment period of the Phase 2 trial. This will position us well to execute on our Phase 3 trial, which is expected to start later this year. Importantly, the new 4-month PANLAR data provide further evidence that our SVP-Rapamycin platform has the ability to induce immune tolerance, with 91% of evaluable patients maintaining serum uric acid level control after being dosed with pegsiticase only in month three versus 17% who receive pegsiticase without previously receiving the three-monthly doses of SEL-212. We believe this evidence of immune tolerance to a highly immunogenic enzyme has positive implications for the overall platform and its potential for combination with other immunogenic biologic therapies.”

Approximately 25% of the patient population treated with SEL-212 in the ongoing Phase 2 trial experienced gout flares during the first month after treatment with continued reduction of gout flare rates over months two to five. This low rate of gout flares appears to be in contrast with higher incidence of gout flares reported in clinical trials involving other urate lowering therapies.

SEL-212 has been generally well tolerated at clinically active doses following repeated administrations in the trial. There have been 15 serious adverse events (SAEs) reported, seven of which were reported to be not related or unlikely to be related to study drug, seven were infusion reactions that were previously reported by the company in its June 2017 data readout, and one infusion reaction in the most recent cohorts. No infusion reactions have been reported after treatment period 2. All SAEs were successfully treated without further issues.